Electroprecipitator



.Oct. 28, 1958 v. J. LENGER ELECTROPRECIPITATOR 2 Sheets-Sheet 1 Filed July 22, 1955 W WWW/W m Y W/ Y Q\ N m Oct. 28, 1958 v. J. LENGER 2,857,978

ELECTROPRECIP TTATOR Filed July 22, 1955 2 Sheets-Sheet 2 Y @M N/ United States Patent 2',5"7,97' ELECTROPRECIPITATOR Vladimir J. L'e'ngi', Prague, Czechoslovakia Application July 22, 1955, Serial No. 523,740 Claiins priority, application Czechoslovakia july 23 195 1 6 Claims. c1. res -1 This invention relates to the testing of air contaminated with aerosols, that is, with suspended fine solid or liquid particles, such as, dust, smoke or fumes, and is particularly directed to a suitable device for such testing.

Among all kinds of devices available for determining the content of solid or liquid particles suspended in air, elect'roprecipitators sho'w maximal efiiciency; The known electroprecipitators includefixed tilbu'lar coaxial electrodes and means for passing a measured a'r'nount of the tested air passing between them so that the charged particles are precipitated on the anode surface. The known electroprecipitators are useful only for aerosol concentrations 8.10 or lower; their e'fficiency being rapidly decreased by the deposit precipitated on the anode surface; The low conductivity of the deposit increasingly interferes with the transfer of the charges and the efi'iciency declines soon to 50"3() percent of the optimal value. This decrease in efliciency is caused by the fact that part of the particles, particularly the heavier particles, pass the space betweeh the electrodes with the air stream without being surficiently charged and captured on the anode. Thus, the results obtained in strongly contaminated air are nineliable. Air must be passed through the e1eetrop're'cipi tator for a sufiic'i'ent period of time in order to secu e the testing of an average sample, and precise determination of the degree of contamination requires the maintenance of optimal conditions for reeipitatidn throughout the test period.

An object of the present invention is to secure the more reliable testihg of the air particularl in industrial work rooms, mines and the like, which may be coma hated with dust of various chemicals; with more, mineral acid fumes, fine silica oi radio active dust. Another eeject of this invention is to provide an improved, mere reliable and readily employed instrument for testing air contaminated with aerosols of various kinds;

In accordance with this invention an electroprecipitator is provided with two electrodes having different lengths, at; least one of which is periodically or continually shifted with respect to theother in parallel direction, in order to always expose to the passed air an anode surface which is not coatedwith a heavy layer of precipitated particles and thus has a constantly high precipi- 7 tating activity which is not reduced by a comparatively thick layer of the precipitated particlcs; In an advantageous embodiment of the invention the anode is in the to the aee'oiiipenyiiig drawings, Whcfihi In the preferred etnbodii'neht bf the iiiventioii the risen ionization cathode is combined with a thermoele tric cathode, and both cathodes have the same voltag finpressed thereon, the thermoelectric cathode forln'ifi'g' a thermal barrier for the particles of the aerosol.

The device according to this invention is suitable testing air of both low and high aerosol par icle centrations ineliid'i'r radioactive sm ke and The sample of the precipitated particles on the ihner stirred: at the iiiter'changeahle tubular aii'ode may be ubjeet'ii t6 "gi'avihietric, ltdnimetric' 'or iadiophy'sial analy s The ihventio'n will be further (retained with ieferenee Fig; 1 islaii elv'atjioiial view, par y 7 iii loii'git Hiiialsectitm bf Edi elebtiopieeipiiatdr embodyiiig this invented; v c c g g M Fig; -2 is a new similar to that Figl, but showiii g another embodimentof the in eritioii; and l v v is, 3 i enlarged 'sctiona'l detail view shb a siiitahle rin'echj ieal means for efleetin'g relative ihdvetheater the electrodes of the d feviee's iii Figs. 1 an Referriirg in retail to Fig, l of the drawing's itfjill be seen that the electi-t'jprecipit'atbr there illiistifa'ted idiudes a ho'using er ca'sirig iii the termere rigid barrel {thavi'iiga p grip 4 1 at one end, A tubular s 3 able wit 1n the Barrel 4, and an iiitereha tubula'r anod' 6, which iiiay he made 'o fi sheet e1 mg a thicknessof 0J6 to' 1.0 is refno y 'f- (1 within the sleeve 3 arid iioriiially moves was later. v A radial pin- 8 projeets from the slee 3 a helical gieeve b'r slot 851 in the suppeitin' bariet dy 4 'so that the sleeve 3 and the anode mounted therein can be displaced along the barrel either by rnaiiiiall'y advaheifig the 8 along groove Qaorby mechaiiical connectioii between ithe sleeye 3 and, a motor 10 mounted within the handle end of barrel Fig. 3 shows, merely by waypf example; a suitablc mechanical connection for efieeting di'splacement ofthe sleeve 'zg along barrel 4 in response to operation of motor 19, and which-includes an axial 1 extension 3a on the sleeve 3 and a hollow motor shaft 13,;telescopically receiving the extension 3;: and connected to the latter, ibr example, by a key,and slot connection 14-, so that the extension 3a and sleeve ,3 are rotated when motor, :10 is operated. Since the pin 8 is received in, the helical groove 8a of barrel ,4, the rotation of sleeve 3 causes the pin to move along the helical groove or slot and thereby effects axial displacement of the sleeve 3 carrying anode 6 withrespect to barrel 4; r,

The electroprecipitator. of Fig. 1 further includes a cathode 1-, 2 having a length which is substantially less than that, of the cathode 6 and a smaller diameter than the internal diameter of the anode so that, when the cathode is mounted coaxially Within the anode; as shown, anannnlar space iscreated thereb'twen throfrgh which the air to Eetested is made to new by an axialfan 9 mounted on the shaft of motor 10 and adapted to dose a constant rate of air new. Thee'athode 1, 2 is mounted at the end of an insulating support member 5 which extends from a socket 7 carried Within the barrel 4 at the end of the latter adjacent motor 10.

When operated manually, the anode 6 is shifted parallel to the direction of the axis of the cathode 1, 2 at certain periods of time during the testing of the air by rotating the pin 8 so that the latter moves along the groove 8a, and the position of the anode relative to the cathode can be observed by suitable markings applied to the barrel 4 and cooperating with the pin 8. A semiconductor anemometer 12 may be placed within barrel 4 adjacent fan 9 for checking the amount of the air passed through the precipitator. The instrument is put in operation by means the of a switch 11 which is interposed in a conventional electrical circuit for the motor 10.

Since the cathode 1, 2 has an axial length substantially :less than that of the anode 6, the aerosol particles are precipitated onto only that .portion of the anode which is axially coextensive with the cathode at any instant. Thus,

,as the anode 6 is axially displaced, either manually or mechanically in response to operation of fan 9 by motor 10, as

described above, successive portions of the anode are disposed axially coextensive with the cathode to receive the precipitated aerosol particles. Accordingly, as a layer of aerosol particles is deposited on a portion of the anode,

the latter moves axially relative to the cathode to dispose an uncoated portion of the anode along the axial length of the cathode so that the precipitating efiiciency of the device is not impaired by the build-up of the layer of precipitated particles and may be maintained at a uniformly high value throughout the test period, thereby ensuring that the amount of aerosol particles on the anode at the end of the test period is an accurate measure of the contamination of the tested air.

Referring now to Fig. 2, it will be seen that the electro- "precipitator there illustrated is generally similar to that described above with reference to Fig. 1, and that the parts thereof are identified by the same reference numerals employed in connection with the corresponding parts of Fig. 1. The electroprecipitator of Fig. 2 differ from that of 'Fig. 1 only in that the cathode of the device of Fig. 2 includes the usual ionization cathode 1a and, in addition thereto, a hot thermoelectric cathode 2a for increasing the thermal gradient between the anode 6 and the cathode 1a, 2a, and for correspondingly increasing the force acting on the particles in the tested air, which force is directly proportional to the thermal gradient.

The drawings represent only two specific examples of the invention which is not limited thereto. It is clear 'that the same eifect may be obtained if the anode is fixed 'spaced radially inward from the latter to define an annular passage between said inner and outer electrodes, one

of said electrodes being substantially longer than the other of said electrodes, mean for causing a flow of the air to be tested through said annular passage while an electrostatic field and an ionization field are created between said electrodes so that aerosol particles contained in the air are charged and deposited on that portion of said one electrode which is then coextensive with the length of said other electrode, said electrodes being axially movable with re spect to each other, and means for effecting axial, relative movement of said electrodes during the flow of air to be tested through said annular passage so that successive portions of said one electrode are disposed coextensive with .the length of said other electrode to successively receive particles precipitated from the tested air and thereby maintain a relatively high precipitating efficiency.

2. An electroprecipitator for testing air contaminated with aerosol particles, comprising an inner, fixed tubular cathode having a rectilinear axis, an outer interchangeable tubular anode coaxially receiving said cathode and having I an internal diameter greater than the external diameter of said cathode to define an annular passage therebetween, said anode being substantially longer than said cathode and axially movable with respect to the latter, an electric motor, fan means driven by said motor and operative to cause a flow of air to be tested through said annular passage while an ionization field and an electrostatic field are created between said cathode and anode so that aerosol particles contained in the airflow are charged and deposited on that portion of said anode which is then axially coextensive with said cathode, and means for axially displacing said anode relative to said cathode during the flow of air through said annular passage so that successive portions of said anode are disposed axially coextensive with said cathode to successively receive particles precipitated from the tested air and thereby maintain a relatively high precipitating etficiency.

3. An electroprecipitator as in claim 2; wherein said cathode includes an electrically heated tubular thermoelectric cathode and an ionization cathode.

4. An electroprecipitator as in claim 2; wherein said means for axially displacing the anode relative to the cathode includes a hollow support surrounding said tubular anode and having a helical slot therein, and a radial pin extending from said anode through said slot for manual movement along the latter so that the anode is axially displaced in response to turning thereof by said pin.

5. An electroprecipitator as in claim 1; wherein said means for causing a flow of air through said annular passage includes a fan and an electric motor for driving said fan; and said means for effecting axial relative movement of said electrodes includes a mechanical connection between said motor and an electrode operative to cause axial displacement of the latter in response to operaiton of said fan.

6. An electroprecipitator as in claim 1; wherein said means for causing a flow of air through said annular References Cited in the file of this patent UNITED STATES PATENTS -l,365,978 Gallager Jan. 18, 1921 1,444,845 McGee Feb. 13, 1923 1,575,165 Hopkinson Mar. 2, 1926 2,307,602 Penney et a1. a Jan. 5, 1943 2,409,579 Meston Oct. 15, 1946 2,484,202 Wintermute Oct. 11, 1949 2,637,408 Yadofi May 5, 1953 

